1. Field of the Invention
The present invention relates to a cross coil-shaped indicating instrument and, more particularly, to a cross coil-shaped indicating instrument suitably used for the speedometer of an automobile or the like.
2. Description of the Related Art
A number of indicating instruments for automobiles have hitherto been employed in which an electric current, whose quantity is altered in correspondence to the amount measured, is passed to a pair of coils that generate magnetic fields perpendicular to each other. A magnet rotor is rotated in a direction of a composite magnetic field composed of the magnetic fields generated by the pair of coils. A pointer attached to a rotary shaft at one end thereof indicates the amount measured, the rotary shaft being rotatable together with the magnet rotor.
To fix the pointer of such a conventional type of indicating instrument to the rotary shaft, first, the rotary shaft is temporarily pressed into the pointer. Under this condition, an electric current equal to a predetermined rotation angle is fed to a cross coil. In the case of, for instance, a speedometer, an electric current corresponding to, for example, 40 km/hour, is supplied. While the electric current is being supplied and the rotary shaft remains stationary, the position of the pointer is adjusted so that it indicates an indicating position of an indicator face. While such a position of the pointer is being maintained, the rotary shaft is pressed into the pointer The appropriately adjusted position of the pointer can thus be maintained.
As mentioned above, an electric current equal to the predetermined rotation angle is fed to the cross coil of the conventional indicating instrument. While the rotary shaft is being maintained at a predetermined rotation position by only the magnetic force of the cross coil, the position of the pointer is adjusted After this adjustment has been made, the rotary shaft is pressed into the pointer. Therefore, when the external peripheral surface of the rotary shaft or the internal surface of the pointer, into which the rotary shaft is pressed, is damaged, it is difficult for the pointer to be fitted onto the rotary shaft due to this damage; or when a pressure load deviates from the center of the rotary shaft, the rotary shaft is pressed into the pointer while the former is rotated slightly with respect to the appropriate position of the latter in response to the pressure load As a result, the pointer is fixed to a position deviating from the predetermined indicating position, rendering the indication characteristics inaccurate and making it impossible to accurately indicate the amount measured.
The present invention has been made in view of the above problems. The object of the invention is therefore to provide a cross coil-shaped indicating instrument which is capable of being pressed into an appropriate position with respect to a rotary shaft and of obtaining accurate indication characteristics.